Ester lubricant compositions

ABSTRACT

ESTER LUBRICANT COMPOSITIONS ARE PROVIDED WHICH PROVIDE A GOOD BALANCE OF LUBRICITY AND EMULSIFIABILITY. THE ESTERS ARE DERIVED FROM POLYOXYALKYLENE GLYCOLS WITH A DIBASIC ACID MIXTURE CONSISTING OF DIMER ACIDS AND SHORTCHAIN DIBASIC ACIDS. CLEAR, HOMOGENEOUS LUBRICANT SOLUTIONS ARE ALSO PROVIDED.

United States Patent 3,769,215 ESTER LUBRICANT COMPOSITIONS Robert J.Sturwold and Fred 0. Barrett, Cincinnati, Ohio, assignors to EmeryIndustries, Inc., Cincinnati, Ohio N0 Drawing. Filed Feb. 4, 1972, Ser.No. 223,752 Int. Cl. C07c 69/34; C10m 1/06 U.S. Cl. 252-495 12 ClaimsABSTRACT OF THE DISCLOSURE Ester lubricant compositions are providedwhich provide a good balance of lubricity and emulsifiability. Theesters are derived from polyoxyalkylene glycols with a dibasic acidmixture consisting of dimer acids and shortchain dibasic acids. Clear,homogeneous lubricant solutions are also provided.

BACKGROUND OF THE INVENTION The use of oils, both natural and synthetic,as lubricants for the working of metals is well-established throughoutthe industry. Straight or uncompounded mineral, vegetable and animaloils have been employed for metal-working but they are not completelysatisfactory berause they lack the cooling properties necessary for manyoperations such as the hot rolling of metals. The recent trend has beentoward the use of aqueous lubricant systems to overcome the coolingproblem as well as other problems associated with the use of straightoils. Typically, aqueous emulsions containing from about 0.1 to 25% ofan emulsifiable oil are employed.

Numerous synthetic lubricants including ether compounds, esters andpolyesters, silicones and hydrocarbon polymers have been proposed toovercome the problems associated with the use of the natural oils andsome of these are useful in aqueous systems. Many of the syntheticlubricants, however, are not readily emulsifiable with water and if anemulsion can be formed, with or without the use of additional additives,most of these emulsions begin to separate after a very short time.

Synthetic lubricants derived from dimer acids such as obtained by thedimerization of oleic acid, linoleic acid or the like have beendescribed in U.S. Pats. Nos. 2,767,- 144 and 3,233,635. While extremelyeffective lubricants can be obtained through the use of dimer acids, thecompatibility of the dimer-based lubricant with Water is generally verypoor. A dimer-based synthetic polyester lubricant having increasedhydrophilic character and useful in aqueous systems is disclosed in U.S.Pat. No. 3,492,- 232. The polyester is derived from the reaction of 0.8to 2.0 mols, and more preferably 1.0 to 1.5 mols, polyoxyalkylene glycolhaving a degree of polymerization of 4 to 200 and 1 mol of a dimer of Cto C fatty acid. While the polyester compositions of the 3,492,232patent present a significant advance in the technology of dimerbasedlubricants they are not without certain disadvantages. The resultingaqueous emulsions are relatively unstable and undergo partial phaseseparation Within a very short period. Furthermore, many of thepolyesters cannot be satisfactorily emulsified without the use ofadditional emulsifying agents of the cationic and nonionic types.Employing additional emulsifier increases the cost of the lubricantcomposition in addition to adding another process variable and istherefore undesirable. The stability of the emulsions can be improvedthrough the use of higher molecular weight polyoxyalkylene glycols withthe dimer, but while the use of these high molecular weightpolyoxyalkylene glycols improves the physical characteristic of theemulsion it severely reduces the lubricating efiiciency of thecomposition since the weight percent dimer acid incorporated therein isproportionately decreased.

It would be highly advantageous to have dimer acidderived syntheticlubricants which are readily emulsifiable with water and are usefullubricants for working of both ferrous and nonferrous metals. It wouldbe especially advantageous if stable emulsions could be formed withoutthe use of external emulsifying aids and simply by moderately agitatingthe synthetic lubricant with cold tap water. Additional benefit would bederived if synthetic lubricants employing low molecular weightpolyoxyalkylene glycols with dimer acid could be prepared so that a highweight percent dimer acid could be obtained; if these lubricants werereadily emulsifiable without the use of external emulsifying agents; andif the resulting emulsions were stable.

SUMMARY OF THE INVENTION We have now discovered that improved esterlubricant compositions derived from dimer acid and polyoxyalkyleneglycols are obtained by incorporating therein an amount of short-chaindibasic acid. The ester mixtures of this invention are more readilyemulsifiable with water than polyesters derived from dimer acid andpo-lyoxyalkylene glycol but not modified with the short-chain dibasicacid. Stable emulsions are obtained with the lubricant compositions ofthis invention without the use of external emulsifying aids. Quiteunexpectedly it has been found that the incorporation of the short-chaindibasic acid permits the use of low molecular weight polyoxyalkyleneglycols with the dimer acid and that the resulting mixed estercompositions, in addition to having increased lubricity as a result ofthe high weight percent dimer acid present, also have superioremulsification properties. This invention provides synthetic esterlubricants which have a good balance of emulsification and lubricationproperties. A further advantage and completely unexpected result is thediscovery that clear, homogeneous lubricant solutions can be preparedwhen the molar ratio of the polyoxyalkylene glycol, dimer acid andshort-chain dibasic acid is within certain defined limits.

The ester lubricants of the present invention are obtained by thecondensation reaction of polyoxyalkylene glycols having molecularweights ranging from 300 to 4000 and more preferably in the range 400 to1000, a dimer acid containing from about 32 to 54 carbon atoms and ashort-chain dibasic acid containing from 2 to 12 carbon atoms and morepreferably from about 6 to 10 carbon atoms. The molar ratio of dibasicacids (dimer acid plus short-chain dibasic acid) to polyoxyal-kyleneglycol will be 1:1.5-2.1. The dimer acid will constitute from about 95to 5 mol percent of the total dibasic acid while the short-chain dibasicacid will range from about 5 to 95 mol percent. Excellent results areobtained when about to 20 mol percent of the total dibasic acid isshort-chain dibasic acid. To obtain water-soluble ester lubricants about7.5 to about 20% by weight short-chain dibasic acid, based on theoverall ester composition, is employed. The water-soluble ester productshave acid values of about 15 or below. The concentration of the ester inaqueous emulsions or solutions useful as lubricants will generally rangefrom about 0.1 to 25% by weight of the lubricant composition.

DETAILED DESCRIPTION The ester lubricants of this invention arecondensation products of polyoxyalkylene glycols with a mixture ofdibasic acids and short-chain dibasic acids. These ester compositionsare useful as lubricants and are readily emulsifiable with water withoutthe addition of external emulsifying agents.

To obtain the lubricant esters of this invention, a polyoxyalkyleneglycol having a molecular weight from about 300 to about 4000, and morepreferably from 400 to 1000, is employed. The recurring alkylene groupsmay contain 2 to 4 carbon atoms and useful polyoxyalkylene glycolshaving varying degrees of polymerization include: polyethylene glycols,polypropylene glycols, polybutylene glycols, poly(ethylenepropylene)glycols and the like. Polyethylene glycols having molecular weights from400 to about 1000 are especially useful and are available fromcommercial suppliers under the trade designations Carbowax and Polyox orthey may be synthesized in the conventional manner. The molecularweights recited above indicate the average molecular weight of thepolyoxyalkylene glycol and it is understood that these compositions aremixtures of polyoxyalkylene glycols having widely divergent molecularweights. Polyoxyalkylene glycols having molecular weights less thanabout 300 or greater than about 4000 should not, however, be present insignificant amounts.

Condensed with the polyoxyalkylene glycol is a mixture of dibasic acidsconsisting of dimer acid and shortchain dibasic acid. The molar ratio ofthe dibasic acids, including both the dimer acid and the short-chaindibasic acid, to the polyoxyalkylene glycol will range from about1:1.52.1 with exceptional results being obtained when the molar ratio is1:1.75-2.0. The proportion of dimer and short-chain dibasic acids may bewidely varied.

Useful dimer acids for the compositions of this invention will containfrom about 32 to 54 carbon atoms. The dibasic acids may be obtained byprocesses known to the art, however, they are most frequently obtainedby the polymerization of monocarboxylic acids containing ethylenicunsaturation. The monocarboxylic unsaturated acids generally containfrom about 16 to 26 carbon atoms and include, for example, oleic acid,linoleic acid, eleostearic acid and similar singly or doubly unsaturatedacids. To obtain the preferred dimer acids 2 mols of the unsaturatedmonocarboxylic acid are reacted, i.e., dimerized. If the resulting dimeracid contains ethylenic unsaturation it may be beneficial to hydrogenateit to obtain the saturated material prior to reaction with thepolyoxyalkylene glycol. Mixtures of dimer acids may be employed. Trimerand tetramer acids may also be present with the dimer acid and do notadversely affect the lubricant properties of the resulting estercompositions so long as about 50% by weight of the mixture arepolymerized acids. Commercially available compositions sold under thetrademark Empol, mixtures of polymerized fatty acids with dimer acid asthe major constituent, may be advantageously employed. Especially usefulare mixed acid products which will contain 75 weight percent or moredimer acid with the remainder being unpolymerized fatty acids or morehighly polymerized acids such as trimer acids.

The short-chain dibasic acid will contain from 2 to about 12 carbonatoms. Short-chain dibasic acids containing 610 carbon atoms areespecially preferred for the present invention. Typical short-chaindibasic acids include oxalic acid, malonic acid, succinic acid, glutaricacid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid andthe like. Mixtures of one or more short-chain dibasic acids may be used.

The dibasic acid mixture consists of about 95 to mol percent dimer acidswith about 5 to 95 mol percent of one or more short-chain dibasic acids.Preferred ester lubricant compositions contain from about 80 to molpercent short-chain dibasic acid and from 90 to 20 mol percent of thedimer.

The condensation of the polyoxyalkylene glycol with the dimer andshort-chain dibasic acids is conducted employing conventionalesterification techniques, that is, by heating the reaction mixture withor without a catalyst at a temperature from about 100 to 300 C. whileremoving the water of reaction. The reactions are most gene a y o uc dever the e p rat re r ge 1 .5 o 250 C. It is not necessary that acatalyst be employed for the esterification reaction, however,conventional acid catalysts such as sulfuric acid, alkyl and arylsulfonic acids such as p-toluene sulfonic acid, phosphorous acids or thelike may be employed. The reaction may be carried out in a diluent whichis inert to the reaction conditions employed and which, preferably, willform an azeotrope with water to facilitate the removal of the water ofreaction. The amount of reactants employed is in accordance with themolar ratios set forth above. For preparation of suitable esterlubricants it is undesirable for the esterification reaction to be lessthan about 70% complete, that is, 70% or more of the carboxyl groupsshould be reacted. The reaction is more generally continued toapproximately completion. This may be determined by measurement of theacid value or hydroxyl value or by measuring the amount of waterevolved. For the preparation of certain preferred ester lubricants whichare water-soluble it is preferred that the reaction be continued untilit is complete or even higher or in terms of acid value, the reactionmixture has an acid value of about 15 or below.

As an alternative procedure for the preparation of the present esterlubricants, the dimer and short-chain dibasic acid may be reacted in thepresence of ethylene oxide. In this way the polyoxyethylene glycol wouldbe prepared in situ. Suitable catalysts and diluents could be added. Itis generally found, however, that more uniform control of molecularweight of the products is obtained when the polyoxyethylene glycol isseparately prepared.

Small amounts of other compounds capable of entering into the reactionmay also be included with the polyoxyalkylene glycol, dimer andshort-chain dibasic acid and are within the scope of the presentinvention. Aromatic dibasic acids, diols and polyols, diamines andpolyamines may be employed in amounts which do not detract from theemulsification and lubrication properties to modify the resultinglubricant composition. For example, the use of diamines, such asdimethylaminopropylamine, may be desirable to enhance the anticorrosionproperties of the lubricant. The amount of these materials will notexceed about 10% and more preferably 5% by weight of the overall estercomposition.

The ester compositions of the present invention provide a convenientmeans to obtain a good balance of lubrication and emulsificationproperties which was not previously possible when polyoxyalkyleneglycols were simply reacted with dimer acids without the addition ofshort-chain dibasic acids. To achieve good lubrication properties withthe prior art polyesters would require that the emulsificationproperties be comprised. Even if additional external emulsifying aidswere added, the resulting emulsions were not always completelysatisfactory and in most instances they would begin to separate after avery short time. Acceptable emulsions can be produced employing theteachings of the prior art if the amount of dimer acid is diminished,however, this results in a marked decrease in the lubrication propertiesand the emulsions are no longer acceptable for metal working. Forexample, a polyester prepared by the condensation of dimer acid with apolyethylene glycol of molecular weight 2000 or greater in accordancewith prior art procedure would form an acceptable emulsion, but thelubrication properties would be inferior and not completely acceptablefor most applications. If. in accordance with the prior art precedure, apolyester was formed from a dimer acid and a polyethylene glycol of lowmolecular weight, say about 400, the lubrication properties of thepolyester would be greatly enhanced but the material would not emulsifyreadily and/or the emulsion would not be stable.

In accordance with the present invention we have prepared mixed esterlubricants which are, at the same time, readily emulsifiable andexcellent lubricants. This is accomplished by replacing a portion of thedimer acid with a short-chain dibasic acid. In this way lower molecularweight polyoxyalkylene glycols can be employed without reducing thehydrophilic character of the resulting ester and the emulsifiability iscomparable or superior to compositions containing much largerproportions of the hydrophilic moiety. Also by the use of low molecularweight polyoxyalkylene glycols, the weight percent of dimer acid presentin the resulting ester mixture may be proportionately increased with theresult that the lubricity of the eser compositions is markedly enhanced.Thus, the present ester lubricant compositions provide the properbalance of dimer (which contributes to the lubricity) andpolyoxyalkylene glycol (which contributes to the emulsifiability) sothat exceptionally useful products are obtained. When very highmolecular weight polyoxyalkylene glycols are reacted with dimer acid inthe absence of a short-chain dibasic acid the lubrication properties ofthe resulting ester products are impaired. Similarly, when very lowmolecular weight polyoxyalkylene glycols are employed theemulsifiability is poor and the product unacceptable.

While the ability of the present invention to provide ester compositionshaving excellent lubricating and emulsifying properties is in itselfvery useful, a preferred embodiment of this invention is even moreadvantageous since it provides completely water-soluble esterlubricants. The water solutions are clear and homogeneous in allproportions. To obtain the water-soluble ester compositions thelubricant ester will contain from about 7.5 to about 20% by weight ofthe short-chain disbasic acid and have an acid value of about or below.Acid values above about 15 are unacceptable if clear solutions are to beobtained. If it is unexpected that as the acid value of the estercomposition is decreased the water solubility or hydrophilic characterof the esters is increased. The solutions produced in accordance withthis preferred embodiment are stable and do not discolor or becomecloudy upon standing. The esters have excellent lubricity in addi tionto being completely water-soluble and may be successfully used invarious metalworking operations.

The lubricants of the present invention are useful in metalworkingoperating as 'aqueous emulsions or as the clear aqueous solutions. Theconcentration of the ester will generally range from about 0.1 to about25% by weight of the lubricant composition although these esters mixwith water in all proportions. The lubrican formulations are added tothe metalworking elements such as the working rolls or the metal itselfby spraying or with other similar equipment. They form a uniform,continuous lubricant film between the working roll and the metal. Theselubricants are useful for Working both ferrous and nonferrous metals.They may be formulated with other additives such as stabilizers,corrosion inhibitors or the like.

The following examples illustrate the improved ester lubricants of thisinvention more fully, however, the examples are not intended to limitthe scope of the invention. All parts and percentages in the examplesare given on a weight basis unless it is otherwise stated.

Example I To a glass reactor equipped with a stirrer, thermometer andwater trap were charged 1030 grams (0.9 equivalent ratio) of dimer acid(Empol 1018 containing 83% C dibasic acid). 37.6 grams (0.1 equivalentratio) azelaic acid and 1600 grams (2.0 equivalents ratio) polyethyleneglycol having an average molecular weight of 400. The reaction mixturewas heated with stirring to about 200 C. and held for approximately 4hours during which time 51 mls. of water were removed. A vacuum of about1 torr was pulled on the system to remove additional water of reaction.After one hour the reaction mixture was sampled and had an acid value ofabout 15.5. Heating was continued under vacuum for four more hoursbefore the reaction mixture was cooled and poured up. The resulting 6lubricant ester composition had a final acid value of 6.7, hydroxylvalue of 93.1, viscosities (ASTM D 445-65) at F. and 210 F. of 548 es.and 70.4 cs., respectively, and flash and fire points (ASTM D 92-66) of555 F. and 605 F., respectively.

A portion (20 mls.) of the ester composition was poured into 100 mls. ofcold tap water while stirring with a glass rod. An emulsion wasimmediately obtained. This emulsion was stable and showed no signs ofphase separation after standing 48 hours at room temperature. Even aftera weeks time the emulsion appeared homogeneous. A sample preparedidentically but with the azelaic acid excluded from the mixture was onlydiflicultly emulsifiable. To obtain an emulstion required vigorousagitation with a mechanical stirrer. When this emulsion was allowed tostand at room temperature there was appreciable phase separation afteronly 24 hours with significant amounts of the oil settling to the bottomof the beaker.

To demonstrate the effectiveness of the ester compositions of thisinvention as lubricants they were evaluated with a Falex machine. Thismachine provides a convenient and reliable means to determine the filmstrength or load-carrying properties of materials as extreme pressuresare applied. Falex testing is recognized throughout the industry as ameans of measuring the relative effectiveness of various lubricants. TheFalex wear test (ASTM D 2670-67) employs a 60 gram sample when thestraight ester is being evaluated. A 600 gram sample is used whenaqueous emulsions or solutions of the ester are to be tested. Theloading device is attached and the cupcontaining the sample beingevaluated positioned so that the steel pin and blocks are completelyimmersed in the sample. The load is then increased to 350 lbs. and runfor 5 minutes. After this time the load is further increased to 1000lbs. and maintained for 30 minutes when testing straight oils or onehour when evaluating lubricant emulsions or solutions. Readings aretaken at the beginning of the hour, after thirty minutes, and at the endof the hour and the difference in the readings indicates the amount ofwear.

Three samples of the lubricant ester composition of this example wereevaluated in accordance with the described test procedure. The straightoil was evaluated and also 10% and 5% aqueous emulsions were tested.Test results obtained are as follows:

Sampler Straight ester: Units wear After 30 minutes 18 After 60 minutes30 10% aqueous emulsion: after 30 minutes 154 5% aqueous emulsion: after30 minutes 174 When the above experiment was repeated employing apolyethylene glycol having an average molecular weight of about 800,similar results were obtained. The ester compositions were readilyemulsifiable and the emulsions had excellent stability. A 4% aqueousemulsion of this ester exhibited superior lubricating properties in theFalex test and performed acceptably as a cutting oil with cold steel.

Example II Employing identical reactants and a similar procedure to thatdescribed in Example I, 715 grams (0.5 equivalent ratio) dimer acid, 235grams (0.5 equivalent ratio) azelaic acid and 2000 grams (2.0equivalents ratio) polyethylene glycol were heated at 200 C. for 6 hoursduring which time 55 mls. of water were removed. An additional 10 mls.of water was taken olf after pulling a vacuum on the system for onehour. The ester reaction mixture at this stage had an acid value of 19.8and readily formed an emulsion with water. Additional heating of thereaction mixture for 2 hours under vacuum reduced the acid value to12.1. The ester (containing about 8 weight percent azelaic acid) had ahydroxyl value of viscosity at 100 F. of 316 cs., viscosity at 200 F. of36.6 cs., and

7 flash and fire points of 530 and 585 F., respectively. The esterreadily dissolved in water in all proportions. No cloudiness wasobservedthe resulting solutions were clear and homogeneous.

Falex wear tests gave the following results:

Sample:

Straight ester: Units wear After 30 minutes 30 After 60 minutes 67 10%water solution: after 30 minutes 132 Water solution: after 30 minutes146 Example III A water-soluble ester lubricant containing about 8% byweight adipic acid was obtained from the reaction of 0.4 equivalentdimer acid (83% C dibasic acid), 0.6 equivalent adipic acid and 2.0equivalents polyethylene glycol having a molecular weight of 400. Thereaction was continued until an acid value of 10.3 was achieved. Theresulting ester composition had a viscosity of 163 cs. at 100 F. Theester lubricant mixed with water in all proportions to give clearsolutions. Water solutions containing 10% and 5% of the so-preparedester were evaluated in the Falex test machine and showed only 132 and156 units of wear, respectively, after 30 minutes testing at 1000 psi.

Repeating the above example using 0.5 equivalent dimer acid and 0.5equivalent adipic acid and running the reaction to an acid value of 12.9gave useful ester lubricants. These compositions when mixed with waterdid not give clear solutions but did form stable emulsions without theuse of external emulsifying aids. The emulsions had excellent shelflives and were elfective lubricants.

Example IV When Example I was repeated using 0.7 equivalent dimer acid,0.3 equivalent azelaic acid and 2.0 equivalents polyethylene glycol, auseful ester lubricant composition having an acid value of 9.1 wasobtained. The ester had a viscosity of 425 cs. at 100 F. and was readilyemulsifiable in cold tap water with minimal stirring and withoutaddition of external emulsifying aids. The emulsion so-produced hadexcellent shelf life and was an eflicient lubricant. A 5% aqueousemulsion of this ester gave less than 150 units wear in the Falexmachine after 30 minutes at 1000 p.s.i.

Ester lubricant compositions were also prepared which incorporated up to0.2 equivalent of an amine corrosion inhibitor such as diethanolamine ordimethylaminepropylamine. The presence of these amines significantlyimproved the corrosion properties of the lubricant composition withoutadversely alfccting the emulsion and lubrication characteristics. Insome instances the amines enhance the emulsion properties of the estercomposition even at reduced polyethylene glycol levels.

Example V Example I was repeated using 0.8 equivalent dimer acid, 0.2equivalent azelaic acid and 2 equivalents polyethylene glycol. Thelubricant ester (acid value 15.5) was easily emulsified. Stableemulsions were obtained which were useful cutting oils when used with atungsten carbide bit.

We claim:

1. Improved ester lubricant compositions comprising the condensationproduct of about 1.5 to 2.1 mols polyoxyalkylene glycols havingmolecular weights from about 300 to about 4000 wherein the recurringalkylene groups contain from 2 to 4 carbon atoms and 1 mol of a mixtureof dibasic acids consisting of 5 to 95 mol percent dimer hydrocarbonacids containing 32 to 54 carbon atoms and 95 to 5 mol percentshort-chain dibasic hydrocarbon acids containing 2 to 12 carbon atoms,said compositions having or more of the carboxyl groups reacted.

2. The lubricant composition of claim 1 wherein the dibasic acid mixturecontains from 20 to 90 mol percent short-chain dibasic acids.

3. The lubricant composition of claim 2 wherein the polyoxyalkyleneglycol is a polyethylene glycol of molecular weight 400 to 1000 and theshort-chain dibasic acid contains 6 to 10 carbon atoms.

4. The lubricant composition of claim 3- wherein the mol ratio ofdibasic acids to polyethylene glycol is 1: l.752.0 and greater than ofthe carboxyl groups of the dibasic acids are reacted.

5. The lubricant composition of claim 2 wherein the mol ratio of dibasicacids to polyoxyalkylene glycol is 1:1.752.0 and the acid value is 15 orbelow.

6. The lubricant composition of claim 5 wherein the polyoxyalkyleneglycol is a polyethylene glycol of molecular weight 400 to 1000 and theshort-chain dibasic acid contains 6 to 10 carbon atoms.

7. The lubricant composition of claim 5 wherein the short-chain dibasicacid comprises from about 7.5 to 20 weight percent of the totalcomposition.

8. The lubricant composition of claim 7 wherein the polyoxyalkyleneglycol is polyethylene glycol having a molecular weight 400, theshort-chain dibasic acid is azelaic acid and the dimer acid contains atleast 75% by weight C dibasic acid.

9. An aqueous lubricant composition suitable for metal workingcontaining about 0.1 to 25% by weight mixed esters obtained by thereaction of 1.5 to 2.1 mols polyoxyalkylene glycols having molecularweights from about 300 to 4000 wherein the recurring alkylene groupscontain from 2 to 4 carbon atoms with 1 mol of a mixture of dibasicacids consisting of 5 to 95 mol percent dimer hydrocarbon acidscontaining 32 to 54 carbon atoms and 95 to 5 mol percent short-chaindibasic hydrocarbon acids containing 2 to 12 carbon atoms, said reactionbeing conducted until at least 70% of the carboxyl groups have beenreacted.

10. The aqueous lubricant composition of claim 9 wherein 1.75 to 2.0mols polyethylene glycol of molec ular weight 400 to 1000 are employedand the dibasic acid mixture contains 20 to mol percent short-chaindibasic acids containing 6 to 10 carbon atoms.

11. The aqueous lubricant composition of claim 10 wherein the estercontains from about 7.5 to 20 Weight percent short-chain dibasic acidand has an acid value of 15 or below.

12. The aqueous lubricant composition of claim 11 wherein theshort-chain dibasic acid is azelaic acid and the dimer acid contains atleast 75 by weight C dibasic acid.

References Cited UNITED STATES PATENTS 3,492,232 1/1970 Rosenberg25249.3 3,377,377 4/1968 Kluge et al. 25256.5

PATRICK P. GARVIN, Primary Examiner A. H. METZ, Assistant Examiner US.Cl. X.R. 252--56.5; 260485 G

